Fuse link



March 30, 1943. c. w. BROWN FUSE LINK Filed Nov. 17, 1941 l-llllI.

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Patented Mar. 30, 1943 UNITED `S'I'ATEIS PATLNT OFFICE FUSE LINK Chester W. Brown, Milwaukee, Wis., assignor to Line Material Company, Milwaukee, Wis., a corporation of Delaware Application November 17, 1941, Serial No. 419,367

8 Claims.

This invention relates to fuse-links for the protection of electrical circuits and has to do more particularly with fuses of the expulsion type wherein 'the fuse-link includes a spring designed to eiiectuate or help effectuate a quick separation of conductive parts upon severance of the fusible elementthereby serving quickly to extinguish the ensuing arc.

According to the ,practice heretofore prevailing when a fuse of the type here dealt with blew out it was necessary to replace the entire fuselink-thus scrapping parts which were unimpaired by the blowout and capable of being salvaged for further use if the fuse-section could economically have been replaced in the field. But, insofar as I am aware, it has not previously been thought practicable to make replaceable fuse-sections because therost of such sections would have .to nearly approach the cost of producing an .entire fuse-link having a non-replaceable fuse-section. f

My object is to provide a replaceable fuse-section which is entirely dependable in operation and which can be manufactured and sold so cheaply as to render it substantially more economical to replace a fuse-section than to replace an entire fuse-link when a blow-out occurs.

The novel features of this invention can be most readily pointed cut by referring to the two embodiments thereof illustrated in the accompanying drawing and described in detail hereafter.

In the drawing:

Fig. l. is an elevational view, partly sectionalized, of a fuse cartridge with a fuse-link installed therein;

Fig. 2 is an elevational view of this Vfuse-link with a replaceable fuse-section forming a part thereof-the latter being shown in longitudinal section;

Fig. 3 is a cross-sectional View 'taken alonglthe line 3--3 0f Fig. 2;

Fig- 4 is an elevational view ci the fuse-section of Fig. 2; and

Fig. 5 is a longitudinal sectional View of a second embodiment of the invention.

The fuse cartridge, per se, shown in Fig. l, comprises a tube I of insulating material tothe upper end of which is threaded a metal ferrule II which, in turn, is externally threaded to receive a removable metal cap I2. Secured to the mid-portion of tube Il) is a metal contact sleeve I3 having a binding screw I4 threaded therein.

Inside the cartridge and identified as a whole by reference numeral I is a fuse-link, illustrated in detail in Fig. 2; but in place of which may be substituted the alternative fuse-link of Fig. 5.

The fuse-link of Fig. 2 comprises a terminal portion Iii to the upper end of which is xed a button I'I by means of which the fuse-link is se cured in the cartridge-see Fig. l-and the lower end of which is threaded at I8 to engage an internally threaded sleeve I9.

Below sleeve I9 and removably secured thereto by virtue of the threaded terminal member 20 is a replaceable fuse-section here identified as a whole by reference numeral 2 I.

To the lower end of fuse-section 2| is removably connected a flexible conductive cord 22 which see Fig. l-is designed to be drawn taut and connected to contact terminal I3 by means of binding screw Id-a suitable aperture, not shown, being provided in contact terminal i3 for the reception of conductor cord 22.

The replaceable fuse-section 2| comprises an elongate fusible element 23 having a relatively extenuate mid-section 24, an intermediate portion 2t of enlarged diameter terminating in a head E@ of still larger diameter, and an enlarged lower end '21, The threaded terminal member 2i! is embedded in the fusible metal head 2li and a second threaded terminal member 28 is embedded in the enlargement 2l. Running axially through the extenuate mid-section 24 of the fusible element 23 is a taut strain Wire 29 which is tied to and interconnects the terminal members 2i! and 2S. Strain wire 23 is usually made of chromenickel-iron alloy and is strong enough to withstand the tension to which it is subjected while at l. the same time it has, in conjunction with the fusible metal forming'the extenuate mid-section` 24, a current carrying capacity slightly in excess of the rated capacity of the link.

Bearing at its upper end against a shoulder Sil on the fusible element is a tube 3| of insulating material, usually fiber, which functions as a housing for the extenuate mid-section and also as a housing and guide for a helical ejector spring 32. Telescoped within tube 3| is another tube 33, also of insulating material-usually fiberwhich functions as a spacer and abutment for the upper end ci spring 32, which spring is normally under compression. In the lower end of tube 3| is inserted a tubular plug 34 of insulating material having a flanged head 35 at its lower end. Thetubular plug forms a lower abutment for spring 32.

Threaded to the lower end of terminal member 28 is a tubular sleeve 36 ,which is internally threaded at 3l for the reception of a cord terminal 38 to which is soldered or otherwise connected the flexible conductor cord 22.

Tubular sleeve 36 is pinched fiat at 13B-see enlarged detail in Fig. 3--to form an enlargement and thus a shoulder which presses against the end of plug 34, thereby serving normally to resist the expansive force or spring 32. It will be observed that the force of the spring places the extenuate mid-section of the fusible element, including strain wire 29 under tension and, as will be apparent, a rupture of this extenuate midsection will permit spring 32 to expel plug 34 downwardly, together with the lower portion of the fusible element as well as terminal member 28, sleeve 36, cord terminal 38 and that portion of cord 22 which normally extends into the cartridge tube. The action of the ejector spring is, of course, aided by the explosive force generated by volatilization of the fusible metal when fusion occurs and explosion of the above enumerated parts takes place with considerable abruptnessthus quickly extinguishing the arc which follows severance of the fusible element.

Fuse-section 2l is, obviously, a unitary selfcontained element easily detachable from Sleeve i9 and cord terminal 38 and it will be apparent that no skill and little time is required to detach the separated parts of a blown out fuse-section from the remainder of the fuse-link and replace the same with a new fuseesection. But to make it worthwhile to provide replacement fuse-sections, it is essential that the entire fuse-link be substantially as cheap to manufacture as a fuselink in which the fuse-section is not replaceable and, further, that the cost to consumers of replacement fuse-sections be materially less than the cost of entire fuse-links of conventional design. Both those requirements are met by the present invention because the parts of the replaceable fuse-section are all capable of cheap production and the assembling operations are very quickly and easily performed. The mode of assembly is thought to be self-evident.

In the alternative construction illustrated by Fig. the terminal portion 4U is provided with a button head 4l which serves the same purpose as the button Il of Fig. 2. Terminal portion 40 is internally threaded at its lower end to receive a metal terminal member 42 which forms one terminus of a fusible strain wire 43 and also as a means for centering a tube 44 of insulating material. The latter tube has a flanged lower end 45 which provides a shoulder against which the lower end of a helical ejector spring 46 abuts-said spring enveloping said tube and abutting at its upper end against an insulating washer 4'! which is threaded or otherwise secured to terminal member 42.

Inserted in the lower end of the tube 44 is a second terminal member 48 which is internally threaded at 49 to receive an externally threaded cord terminal 56 which, in turn, is soldered or otherwise secured to the end of a flexible conductor cord 5l. Terminal member 48 is tubular atits lower end and is pinched flat at 52 to provide a shoulder which bears against the lower end of tube 44 and secures the same against the force of spring 46 which is normally under compression.

Terminal members 42 and 48 are both drilled endwise to receive the respective ends of fusible strain wire 43 and, for the purpose of securely anchoring said strain wire to said members the latter are indented at 53 and 54 when the strain wire is in place, thereby firmly clamping down on the ends of the strain wire.

Tube 44 is preferably a free t on terminal member 42 and since spring 46 is normally compressed it will be clear that upon fusion and severance of strain wire 43 said tube and all parts therebelow will be expelled from the fuse cartridge.

Depending upon the current-carrying capacity required, fuses are commonly made with a strain wire embedded in low melting point fusible alloy as shown in Fig. 2 or without the low melting point fusible alloy, as shown in Fig. 5, and it will be evident that in the structure of Fig. 5 the strain wire lcould be embedded in low melting point fusible alloy'if desired, and vice-versa.

What is claimed is;

1. A replaceable fuse-section designed to function as a component part of a fuse-link, said fuse-section being a self-contained unitary structure comprising a tube of insulating material, a fusible element within said tube, an ejector spring co-axial with said tube and continuously applying tension to said fusible element, and a pair of terminal members, one at each end of said tube, said terminal members being connected individually to the respective ends of said fusible element, each said terminal member being provided with means for eilecting readily detachable connection with other fuse-link portions between which said fuse-section is intended to be interposed.

2. A replaceable fuse-section designed to function as a component part of a fuse link, said fuse-section being a self-contained unitary structure comprising a tube of insulating material, an elongate fusible element within said tube and extending longitudinally thereof, a helical ejector spring co-aXial with said tube and at least partially co-extensive therewith lengthwise, said spring continuously applying tension t0 said fusible element, and a pair of terminal members, one at each end of said tube, said terminal members being connected individually to the respective ends of said fusible element, one of said terminal members having a portion which is pinched flat to provide an abutment for securing said tube in place and for resisting the action of said spring, each said terminal member being provided with means for eifecting readily detachable connection with other fuse-link portions between which said fusesection is intended to be interposed.

3. A replaceable fuse-section designed to function as a component part of a fuse-link, said fusesection being a self-contained unitary structure comprising a tube of insulating material, an elongate fusible element within said tube and extending longitudinally thereof, a helical ejector spring coaxial with said tube and at least partially coextensive therewith lengthwise, said spring continuously applying tension to said fusible element, and a pair of terminal members, one at each end of said tube, said terminal members being connected individually to the respective ends of said fusible element, one of said terminal members being tubular for at least a part of itsI length, a portion of said tubular part being collapsed to form an abutment for securing said tube in place and for resisting the force of said spring, each said terminal member being threaded for effecting readily detachable connection with other fuselink portions between which said fuse-section is intended to be interposed.

4. A replaceable fuse-section designed to function as a component part of a fuse-link, said fusesection being a self-contained unitary structure comprising an elongate tube of insulating material, a helical ejector spring within said tube and co-axial therewith, an elon-gate fusible element Within said tube and extending axially through said spring, said fusible element having a shouldered enlargement projecting from one end of said tube and against which the adjacent end yof said tube abuts, a terminal member attached to and projecting from said enlargement, a second terminal member projecting from the end of said tube remote from said enlargement and connected to said fusible element, said last-mentioned terminal member having a shoulder which serves to secure said tube in place and at least indirectly as an abutment for said spring whereby said fusible element is subjected to continuous tension by said spring, each said terminal member being provided with means for effecting readily detachable connection with other fuse-link portions between which said fuse-section is intended to be interposed.

5. A replaceable fuse-section designed to function as a component part of a fuse-link, said fusesection being a self-contained unitary structure comprising an elongate fusible element having an extenuate mid-section and an enlargement at one end having a peripheral shoulder, a tube of insulating material co-axial with and enclosing said extenuate mid-section, said tube bearing at one end against said shoulder, a compressed helical ejector spring within said tube and co-axial therewith, a tubular plug of insulating material inserted in the end of said first tube remote from l said enlargement and abutting one end of said spring, a tubular terminal member inserted in said plug and connected with the end of said fusible element remote `from said enlargement, said terminal member projecting axially from said tube and having a flattened mid-portion pro-- viding an abutment for the external end of said plug whereby to retain said spring in said tube under compression, and a second terminal member attached to said enlargement and projecting axially therefrom, each said terminal member being provided with means for effecting readily detachable connection with other fuse-link portions between which said fuse-section is intended to be interposed.

6. A replaceable fuse-section designed to function as a component part of a fuse-link, said fusesection being a self-contained unitary structure comprising an elongate fusible element havinar an extenuate mid-section and an enlargement at one end having a peripheral shoulder, a tube of insulating material co-axial with and enclosing said extenuate mid-section, said tube bearing at one end against said shoulder, a tubular plug of insulating material inserted in the end of said tube remote from said enlargement, said plug having a peripheral shoulder bearing against the adjacent end of said tube, a compressed helical ejector spring within said tube and co-axial therewith, said spring being interposed between the inner end of said plug and the said shoulder on said enlargement, said spring tending to effect a longitudinal disruption of said fuse-section, a terminal member attached to said enlargement and projecting axially therefrom and a tubular` terminal member inserted in said plug and connected Ywith said fusible element, said tubular terminal f, to said terminal member and forming an abutment for one end of said tube, said washer overlapping the periphery of said tube annularly, a compressed helical ejector spring enveloping said tube and substantially co-extensive therewith longitudinally, said tube having a shoulder at the end thereof remote from said washer and against which said spring abuts, a second terminal member inserted in the end of said tube remote from said first terminal member, a fusible link within said tube interconnecting said terminal members and under tension imposed by said spring, said second terminal member having a shoulder engaging the adjacent end of said tube and serving to retain said spring in place and under compression, each said terminal member projecting axially from said tube and having means for eifecting readily detachable connection with other fuselink portions between which said fuse-section is intended to be interposed.

8. A replaceable fuse-section designed to function as a component part of a fuse-link, said fuse-section being a self-contained unitary structure comprising an elongate tube of insulating material, two terminal members each projecting individually from opposite ends of said tube, a fusible element Within said tub-e interconnecting said terminal members, a compressed helical ejector spring encircling said tube, means defining a non-conductive shoulder connected with one of said terminal members but not connected with said tube and constituting an abutment for one end of said spring, a shoulder on said tube constituting an abutment for the opposite end of said spring, one of said terminal members being tubular, at least in part, a portion of said tubular part being collapsed to form an enlargement for securing together the assembled parts of said fuse-section and for holding said spring under compression, said fuse section being disruptable by said spring upon severance of said fusible element, each said terminal member being threaded for effecting readily detachable connections with other fuse-link portions between which said fusesection is intended to be interposed.

CHESTER W. BROWN. 

